Parabolic reflector press-fits into mounting holes (arrow right image) on either side of the stand.
Epi-illuminating reflector can be positioned to illuminate an opaque specimen.
This Watson camera lucida was included in the mahogany storage case. It has an internal prism (arrow) that covers half the field of view and two ND filters to equalize the light reflecting off the drawing page and the specimen. The desired result would be seeing the specimen superimposed over the drawing paper.
The thumbscrew allows the camera lucida to be positioned appropriately with the drawing page either left or right of the microscope.